Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device includes a semiconductor element, a first conductor bonded to an upper surface of the semiconductor element via a first solder layer, and a second conductor bonded to an upper surface of the first conductor via a second solder layer. The first conductor includes at least one groove formed in a stacking direction of the semiconductor element, the first conductor, and the second conductor on a side surface adjacent to the upper surface of the first conductor.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-009950 filed onJan. 24, 2018 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a semiconductor device and a method ofmanufacturing the same.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2005-136018 (JP2005-136018 A) discloses a semiconductor device. The semiconductordevice includes a semiconductor element, a first conductor bonded to anupper surface of the semiconductor element via a solder layer, and asecond conductor bonded to an upper surface of the first conductor via asolder layer. In the semiconductor device, a groove surrounding thesolder layer is formed on a lower surface of the second conductor, andexcessive solder is accommodated inside the groove. With such aconfiguration, when the first conductor and the second conductor aresoldered therebetween, spreading of excessive solder to an unintendedrange in a wet manner is suppressed.

SUMMARY

In the semiconductor device described above, when the excessive soldercannot be sufficiently absorbed by the groove of the second conductor,the excessive solder spreads in a wet manner along a side surface of thefirst conductor, and the solder is likely to be connected from the uppersurface to the lower surface via the side surface of the firstconductor. In this case, it is easy for a large stress to act on thesemiconductor element from the solder at a portion at which the solderhas been connected. As a result, reliability of the semiconductor devicemay be degraded. The present disclosure provides a semiconductor devicecapable of avoiding or reducing degradation of reliability of asemiconductor device caused by excessive solder and a method ofmanufacturing the semiconductor device.

A first aspect of the present disclosure relates to a semiconductordevice. The semiconductor device includes a semiconductor element, afirst conductor bonded to an upper surface of the semiconductor elementvia a first solder layer, and a second conductor bonded to an uppersurface of the first conductor via a second solder layer. The firstconductor includes at least one groove provided in a stacking directionof the semiconductor element, the first conductor, and the secondconductor on a side surface adjacent to the upper surface of the firstconductor.

In the semiconductor device described above, the at least one grooveextending in the stacking direction of the semiconductor element, thefirst conductor, and the second conductor on the side surface adjacentto the upper surface of the first conductor is provided. According tothe first aspect, when the first conductor and the second conductor aresoldered or when the first conductor and the semiconductor element aresoldered, excessive solder is guided to the grooves formed on the sidesurfaces of the first conductor. That is, a position at which theexcessive solder spreads in a wet manner can be limited to a position atwhich the groove is formed. Therefore, in one example, the position ofthe groove formed on the side surface of the first conductor may be setto a range in which a stress acting on the semiconductor element fromthe solder is inherently small. Accordingly, even when the solder isconnected from the upper surface to the lower surface through the sidesurface of the first conductor, it is possible to avoid an excessivestress acting on the semiconductor element from the solder. Accordingly,it is possible to avoid or reduce degradation of reliability of thesemiconductor device.

In the semiconductor device according to the first aspect, the at leastone groove of the first conductor may extend to at least one of theupper surface and the lower surface of the first conductor. In thiscase, since a solder directly contacts the end portion of the groovewhen soldering is performed on at least one of the upper surface or thelower surface of the first conductor, it is easy for excessive solder tobe guided to the groove formed on the side surface of the firstconductor.

In the semiconductor device according to the aspect, the at least onegroove of the first conductor may extend to one of the upper surface andthe lower surface of the first conductor, and may not extend to theother of the upper surface and the lower surface of the first conductor.That is, a first end portion of the groove may be located on one of theupper surface and the lower surface of the first conductor, and a secondend portion of the groove may be separated from the other of the uppersurface and the lower surface of the first conductor. In this case,since the first end portion of the groove directly contacts the solderon one of the upper surface and the lower surface of the firstconductor, it is easy for excessive solder to be guided to the grooveformed on the side surface of the first conductor. On the other hand,since the second end portion of the groove is separated from the otherof the upper surface and the lower surface of the first conductor, thesolder spreading in a wet manner along the groove reaching the other ofthe upper surface and the lower surface of the first conductor issuppressed. Accordingly, connection of the solder between the firstconductor and the second conductor and the solder between the firstconductor and the semiconductor element along the side surface of thefirst conductor is suppressed.

In the semiconductor device according to the first aspect, the firstconductor may include the at least one groove in a range correspondingto a corner portion of the semiconductor element on the side surface ofthe first conductor. With the above configuration, it is easy forexcessive solder to be guided to a range corresponding to a cornerportion of the semiconductor element (a range including a positionclosest to the corner portion of the semiconductor element). Here, atthe corner portion of the semiconductor element, a stress acting on thesemiconductor element from the solder is inherently small. Therefore,even when the solder is connected from the upper surface to the lowersurface through the side surface of the first conductor, it is possibleto avoid an excessive stress acting on the semiconductor element fromthe solder.

In the semiconductor device according to the aspect, the first conductormay include the at least one groove in at least one corner portion amongfour corner portions of the side surface.

In the semiconductor device according to the aspect, the corner portionmay be chamfered.

In the semiconductor device according to the aspect, the corner portionmay be cut or pressed to have a cross shape when the first conductor isviewed in a plan view.

In the semiconductor device according to the first aspect, the firstconductor may include a plurality of grooves. Accordingly, as the numberof grooves formed in the first conductor becomes larger, a larger amountof excessive solder can be guided to and accommodated in the groove, andan effect of an application of the present disclosure can be furtherenhanced.

In the semiconductor device according to the first aspect, an angleformed by a fillet shape of a solder located between the first conductorand the semiconductor element may be smaller than 90°.

A second aspect of the present disclosure relates to a method ofmanufacturing a semiconductor device. The method includes solder-bondinga first conductor to an upper surface of a semiconductor element to forma laminate, and solder-bonding a second conductor to an upper surface ofthe first conductor in the laminate. The first conductor includes atleast one groove provided in a stacking direction of the laminate on aside surface adjacent to the upper surface of the first conductor, andthe at least one groove extends to the upper surface of the firstconductor. When the second conductor is solder-bonded to the uppersurface of the first conductor, the second conductor is disposed on thelower side of the laminate.

According to the second aspect, when the second conductor issolder-bonded to the upper surface of the first conductor in thelaminate, the solder located between the first conductor and the secondconductor directly contacts the end portion of the groove, andtherefore, it is easy for excessive solder to be guided to the grooveformed on the side surface of the first conductor. On the other hand,since the groove does not extend to the lower surface of the firstconductor (a bonding surface between the first conductor and thesemiconductor element), the solder guided in the groove does not reachthe lower surface of the first conductor, and therefore, connection ofthe solder from the upper surface to the lower surface through the sidesurface of the first conductor is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a cross-sectional view illustrating an internal structure of asemiconductor device of an embodiment;

FIG. 2 is a plan view and a side view of a conductor spacer of asemiconductor device;

FIG. 3 illustrates a first reflow step of laminating a lower heatradiation plate, a semiconductor element, and a conductor spacer in thisorder and forming a laminate by soldering;

FIG. 4 illustrates a step of disposing the laminate on an upper heatradiation plate;

FIG. 5 illustrates a second reflow step of soldering the laminate ontothe upper heat radiation plate;

FIG. 6 schematically illustrates a behavior of a solder located betweena conductor spacer and the upper heat radiation plate in the secondreflow step;

FIG. 7 schematically illustrates a behavior of a solder located betweena conductor spacer and the upper heat radiation plate when a conductorspacer of the related art is used;

FIG. 8 illustrates a state in which a solder is connected over an entireside surface from an upper surface to a lower surface of the conductorspacer of the related art;

FIG. 9A illustrates a modification example in which a position (a cornerportion) at which a groove is provided on a side surface of theconductor spacer is changed;

FIG. 9B illustrates a modification example in which a position (a cornerportion) at which a groove is provided on a side surface of theconductor spacer is changed;

FIG. 9C illustrates a modification example in which a position (a cornerportion) at which a groove is provided on a side surface of theconductor spacer is changed;

FIG. 9D illustrates a modification example in which a position (a cornerportion) at which a groove is provided on a side surface of theconductor spacer is changed;

FIG. 10 illustrates a modification example in which a shape of a cornerportion at which a groove is provided on the side surface of theconductor spacer is changed;

FIG. 11A illustrates a modification example in which a shape of a grooveon the side surface of the conductor spacer is changed;

FIG. 11B illustrates a modification example in which a shape of a grooveon the side surface of the conductor spacer is changed; and

FIG. 11C illustrates a modification example in which a shape of a grooveon the side surface of the conductor spacer is changed.

DETAILED DESCRIPTION OF EMBODIMENTS

A semiconductor device 10 and a method of manufacturing thesemiconductor device 10 of an embodiment will be described withreference to the drawings. The semiconductor device 10 of the embodimentcan be used for a power conversion circuit such as a converter or aninverter in an electrically driven vehicle such as an electric vehicle,a hybrid vehicle, and a fuel cell vehicle. Note that, a use of thesemiconductor device 10 is not particularly limited. The semiconductordevice 10 can be widely adopted for various devices or circuits.

As illustrated in FIG. 1, the semiconductor device 10 includes asemiconductor element 12, a sealing body 30, and a plurality of externalconnection terminals 17, 19, 20. The semiconductor element 12 is sealedinside the sealing body 30. The sealing body 30 is not particularlylimited, but is formed of, for example, a thermosetting resin such as anepoxy resin. Each of the external connection terminals extends from theoutside to the inside of the sealing body 30 and is electricallyconnected inside the sealing body 30. In one example, the externalconnection terminals 17, 19, 20 include power terminals 17, 19 and asignal terminal 20.

The semiconductor element 12 includes an upper surface electrode 12 a, alower surface electrode 12 b, and a signal pad 12 c. The upper surfaceelectrode 12 a and the signal pad 12 c are located on an upper surfaceof the semiconductor element 12 and the lower surface electrode 12 b islocated on a lower surface of the semiconductor element 12. Thesemiconductor element 12 is a vertical semiconductor element having apair of upper and lower electrodes 12 a, 12 b. The semiconductor elementin this embodiment is a power semiconductor element such as ametal-oxide-semiconductor field-effect transistor (MOSFET) or aninsulated gate bipolar transistor (IGBT). Further, the semiconductorelement 12 can be formed of, for example, various semiconductormaterials such as silicon (Si), silicon carbide (SiC), or galliumnitride (GaN). Materials constituting the upper surface electrode 12 a,the lower surface electrode 12 b, and the signal pad 12 c are notparticularly limited, and, for example, aluminum or other metals can beadopted.

The semiconductor device 10 includes a conductor spacer 14, an upperheat radiation plate 16, and a lower heat radiation plate 18. Theconductor spacer 14 is formed of, for example, a material havingconductivity such as copper or another metal. The conductor spacer 14 isgenerally a plate-shaped or block-shaped member and includes an uppersurface 14 a, a lower surface 14 b located on the side opposite to theupper surface 14 a, and four side surfaces 14 c spreading between theupper surface 14 a and the lower surface 14 b. The conductor spacer 14is located inside the sealing body 30. The upper surface 14 a of theconductor spacer 14 is bonded to an upper heat radiation plate 16 to bedescribed below via a solder layer 24. The lower surface 14 b of theconductor spacer 14 is bonded to the upper surface electrode 12 a of thesemiconductor element 12 via a solder layer 26. That is, the conductorspacer 14 is electrically connected to the semiconductor element 12. Theconductor spacer 14 secures a space when the signal terminal 20 isconnected to the semiconductor element 12. Here, the conductor spacer 14is an example of the first conductor. The solder layer 24 is an exampleof the second solder layer and the solder layer 26 is an example of thefirst solder layer.

The upper heat radiation plate 16 and the lower heat radiation plate 18are formed of, for example, a material having excellent thermalconductivity such as copper, aluminum or other metal. The lower heatradiation plate 18 is generally a rectangular parallelepiped orplate-shaped member and includes an upper surface 18 a and a lowersurface 18 b located opposite to the upper surface 18 a. The uppersurface 18 a of the lower heat radiation plate 18 is bonded to the lowersurface electrode 12 b of the semiconductor element 12 via a solderlayer 28. That is, the lower heat radiation plate 18 is electrically andthermally connected to the semiconductor element 12. Accordingly, thelower heat radiation plate 18 not only constitutes a portion of theelectrical circuit of the semiconductor device 10 but also functions asa heat radiation plate that releases the heat of the semiconductorelement 12 to the outside.

The upper heat radiation plate 16 is generally a rectangularparallelepiped or plate-shaped member and includes an upper surface 16 aand a lower surface 16 b located opposite to the upper surface 16 a. Theupper surface 16 a of the upper heat radiation plate 16 is exposed tothe outside of the sealing body 30. The lower surface 16 b of the upperheat radiation plate 16 is bonded to the upper surface 14 a of theconductor spacer 14 via the solder layer 24. That is, the upper heatradiation plate 16 is electrically and thermally connected to thesemiconductor element 12 via the conductor spacer 14. Accordingly, theupper heat radiation plate 16 not only constitutes a portion of theelectrical circuit of the semiconductor device 10, but also functions asa heat radiation plate that releases heat of the semiconductor element12 to the outside. Thus, the semiconductor device 10 of the embodimenthas a double-sided cooling structure in which the upper heat radiationplate 16 and the lower heat radiation plate 18 are exposed to bothsurfaces of the sealing body 30. Here, the upper heat radiation plate 16is an example of the second conductor.

As described above, the semiconductor device 10 includes the powerterminals 17, 19 and the signal terminal 20 as a plurality of externalconnection terminals. In an example, the power terminal 17 is bonded tothe lower surface 16 b of the upper heat radiation plate 16 and thepower terminal 19 is bonded to the upper surface 18 a of the lower heatradiation plate 18. For the bonding, a bonding method using welding orthe like can be adopted. The bonding is not particularly limited, andother bonding scheme may be adopted. In addition, the signal terminal 20is connected to the signal pad 12 c of the semiconductor element 12 viaa bonding wire 22.

A groove 16 c is provided on the lower surface 16 b of the upper heatradiation plate 16 to surround the solder layer 24. When the conductorspacer 14 and the upper heat radiation plate 16 are soldered, it ispossible to suppress, by means of the groove 16 c, accommodation ofexcessive solder and spreading of excessive solder in a wet manner to anunintended range.

However, when excessive solder cannot be sufficiently absorbed by thegroove 16 c of the upper heat radiation plate 16, the excessive soldermay spread in a wet manner along the side surface 14 c of the conductorspacer 14. When the solder is connected from the upper surface 14 a tothe lower surface 14 b through the side surface 14 c of the conductorspacer 14, it is easy for a large stress to act on the semiconductorelement 12 from the solder at a portion at which the solder has beenconnected. As a result, reliability of the semiconductor device 10 islikely to be degraded.

In the present disclosure, as illustrated in FIG. 2, a plurality ofgrooves 14 d is provided on the side surfaces 14 c of the conductorspacer 14. The grooves 14 d extend in the stacking direction of thesemiconductor device 10. With such a configuration, when the conductorspacer 14 and the upper heat radiation plate 16 are soldered or when theconductor spacer 14 and the semiconductor element 12 are soldered,excessive solder is guided to the grooves 14 d formed on the sidesurfaces 14 c of the conductor spacer 14. That is, a position at whichthe excessive solder spreads in a wet manner can be limited to aposition at which the groove 14 d is formed.

Accordingly, in the embodiment, the positions of the grooves 14 d formedon the side surfaces 14 c of the conductor spacer 14 are provided atfour corner portions of the conductor spacer 14, which are rangescorresponding to the four corner portions of the semiconductor element12, as illustrated in FIG. 2. With such a configuration, it is easy forexcessive solder to be guided to ranges corresponding to corner portionsof the semiconductor element 12. Here, the ranges corresponding to thecorner portions of the semiconductor element 12 on the side surfaces 14c of the conductor spacer 14 means ranges including position closest tothe corner portions of the semiconductor element 12, and corresponds toportions located at the four corner portions of the conductor spacer 14in a plan view (see an upper portion of FIG. 2) in the conductor spacer14 of the embodiment. The four corner portions of the conductor spacer14 are chamfered, and the grooves 14 d are provided on chamferedsurfaces. At the corner portions of the semiconductor element 12, astress acting from the solder to the semiconductor element 12 isinherently small. Therefore, even when the solder is connected from theupper surface 14 a to the lower surface 14 b through the side surface 14c of the conductor spacer 14, it is possible to avoid an excessivestress from acting on the semiconductor element 12 from the solder.Accordingly, it is possible to avoid or reduce degradation ofreliability of the semiconductor device 10.

In addition, in an example, the groove 14 d in the side surface 14 c ofthe conductor spacer 14 extends to the upper surface 14 a of theconductor spacer 14 and does not extend to the lower surface 14 b of theconductor spacer 14. That is, an end portion of the groove 14 d on theupper surface 14 a side of the conductor spacer 14 is located on theupper surface 14 a of the conductor spacer 14, and an end portion of thegroove 14 d on the lower surface 16 b side of the conductor spacer 14 isseparated from the lower surface 14 b of the conductor spacer 14. Inthis case, on the upper surface 14 a of the conductor spacer 14, the endportion of the groove 14 d on the upper surface 14 a side of theconductor spacer 14 directly contacts the solder 24, and therefore, itis easy for excessive solder to be guided to the groove 14 d formed inthe side surface 14 c of the conductor spacer 14. On the other hand,since the end portion of the groove 14 d on the side of the lowersurface 14 b of the conductor spacer 14 is separated from the lowersurface 14 b of the conductor spacer 14, and therefore, the solderspreading in a wet manner along the groove 14 d reaching the lowersurface 14 b of the conductor spacer 14 is suppressed. Accordingly,connection of the solder 24 between the conductor spacer 14 and theupper heat radiation plate 16 along the side surface 14 c of theconductor spacer 14 is suppressed. Note that, a direction in which thegroove 14 d extends is not limited to the upper surface 14 a of theconductor spacer 14 and the groove 14 d may extend to the lower surface14 b. In this case, connection of the solder 26 between the conductorspacer 14 and the semiconductor element 12 along the side surface 14 cof the conductor spacer 14 is suppressed. Note that, in anotherembodiment, the groove 14 d may extend from the upper surface 14 a tothe lower surface 14 b of the conductor spacer 14.

Here, the solders 24, 26 constitute the above-described solder layers24, 26, and therefore, description will be given using the samereference numerals. Similarly, solder 28 to be described below alsoconstitutes the above-described solder layer 28, and therefore,description will be given using the same reference numerals.

A method of manufacturing the semiconductor device 10 of the embodimentwill be described with reference to FIGS. 3 to 6. First, the lower heatradiation plate 18, the semiconductor element 12, and the conductorspacer 14 are prepared. Here, a lead frame formed integrally with theexternal connection terminals 19, 20, for example, can be adopted forthe lower heat radiation plate 18. Then, the lower heat radiation plate18, the semiconductor element 12, and the conductor spacer 14 aresequentially arranged, and the respective members are solderedtherebetween to form a laminate X (a first reflow step). In this case,the solder layers 28, 26 are formed between the upper surface 18 a ofthe lower heat radiation plate 18 and the lower surface electrode 12 bof the semiconductor element 12 and between the upper surface electrode12 a of the semiconductor element 12 and the lower surface of theconductor spacer 14, respectively. A solder in a sheet shape can beadopted as an example of the solders 26, 28 disposed between therespective members.

Next, as illustrated in FIG. 4, the laminate X formed in the firstreflow step is inverted on the lower surface 14 b of the prepared upperheat radiation plate 16 and disposed so that the conductor spacer 14becomes on the lower side. After the disposition, as illustrated in FIG.5, the conductor spacer 14 and the upper heat radiation plate 16 aresoldered (a second reflow step). In this case, the solder layer 24 isformed between the lower surface 16 b of the upper heat radiation plate16 and the upper surface 14 a of the conductor spacer 14. For the solder24 disposed between the upper heat radiation plate 16 and the conductorspacer 14, a sheet-shaped solder can be adopted, for example. Here, ithas been found that an angle θ (see FIG. 5) formed by a fillet shape ofthe solder located between the conductor spacer 14 and the semiconductorelement 12 after the second reflow step becomes equal to or greater than90°, reliability of the semiconductor device is greatly degraded.Therefore, it is desirable for the angle θ formed by the fillet shape ofthe solder located between the conductor spacer 14 and the semiconductorelement 12 to be smaller than 90°.

On the other hand, even when the angle θ formed by the fillet shape ofthe solder located between the conductor spacer 14 and the semiconductorelement 12 is equal to or greater than 90°, a position at whichexcessive solder spreads in a wet manner is limited to a position atwhich the groove 14 d has been formed due to the application of thepresent disclosure. Therefore, it is possible to suppress a large stressacting on the semiconductor element 12 from the solder.

In the embodiment, the grooves 14 d of the conductor spacer 14 arelocated at the corner portions of the side surface 14 c of the conductorspacer 14, as described above. Therefore, excessive solder of the solder24 located between the conductor spacer 14 and the upper heat radiationplate 16 is preferentially guided to the range corresponding to thecorner portions of the semiconductor element 12, as illustrated in FIG.6. At the corner portions of the semiconductor element 12, a stressacting on the semiconductor element 12 from the solder is inherentlysmall. Therefore, even when the solder is connected from the uppersurface 14 a to the lower surface 14 b through the side surface 14 c ofthe conductor spacer 14, an excessive stress acting on the semiconductorelement 12 from the solder can be avoided since a range in which theexcessive solder spreads in a wet manner is limited as described above.

In addition, since the grooves 14 d of the conductor spacer 14 in theembodiment do not extend to the lower surface 14 b of the conductorspacer 14 (a bonding surface between the conductor spacer 14 and thesemiconductor element 12), the solder 24 guided to the grooves 14 d doesnot reach the lower surface 14 b of the conductor spacer 14.Accordingly, connection of the solders 24, 26 from the upper surface 14a to the lower surface 14 b through the side surfaces 14 c of theconductor spacer 14 is suppressed.

On the other hand, in a configuration of a semiconductor device of therelated art, excessive solder of the solder 24 located between theconductor spacer 114 and the upper heat radiation plate 16 spreads in awet manner over an entire side surface 114 c of the conductor spacer114, as illustrated in FIG. 7. When the solder 24 further spreads in awet manner, the solder is likely to be connected over the entire sidesurface 114 c from the upper surface 114 a to the lower surface 114 b ofthe conductor spacer 114 (see FIG. 8). As a result, an angle θ formed bya fillet shape of the solder located between the conductor spacer 114and the semiconductor element 12 is equal to or greater than 90°, andreliability of the semiconductor device is greatly degraded. Note that,in this case, an angle at which the excessive solder of the solder 24located between the conductor spacer 14 and the upper heat radiationplate 16 spreads in a wet manner and is connected is also included inthe angle θ formed by the fillet shape of the solder located between theconductor spacer 114 and the semiconductor element 12.

After the second reflow step described above, the semiconductor element12, the conductor spacer 14, the upper heat radiation plate 16, and thelower heat radiation plate 18 are sealed with the sealing body 30. Notethat, for example, when the surfaces 16 a and 18 b of the heat radiationplates 16 and 18 are not exposed after sealing, the surface of thesealing body 30 is ground so that the surfaces 16 a and 18 b of the heatradiation plates 16 and 18 are exposed. Finally, for example, removal ofunneeded portions (for example, a tie bar of the lead frame) isperformed, and the electrical circuit is made independent so that thesemiconductor device 10 is completed.

The position at which the groove 14 d is provided at the corner portionof the side surface 14 c of the conductor spacer 14 in the presentdisclosure can be variously changed. A modification example of theconductor spacer 14 will be described with reference to FIGS. 9A to 9Dand FIG. 10. In the embodiment, the grooves 14 d are provided at all thecorner portions (that is, the four corner portions). Chamfering isperformed by, for example, cutting or pressing, and the groove 14 d isprovided on the chamfered surface. The positions at which the groove 14d is provided is not limited to all the corner portions of the conductorspacer 14, and the groove 14 d may be provided at one corner portion,two corner portions, or three corner portions. A specific example isshown below. The position at which the groove 14 d is provided may beprovided at one of the four corner portions, as illustrated in FIG. 9A.Further, the position at which the groove 14 d is provided may beprovided at two adjacent corner portions of the side surfaces 14 c ofthe conductor spacer 14, as illustrated in FIG. 9B, or may be providedat two corner portions on a diagonal line, as illustrated in FIG. 9C.Further, the position at which the groove 14 d is provided may beprovided at three corner portions, as illustrated in FIG. 9D.

Further, the groove 14 d on the side surface 14 c of the conductorspacer 14 of the embodiment is chamfered by, for example, cutting orpressing at the four corner portions of the conductor spacer 14, and thegroove 14 d is provided on the chamfered surface. However, a shape ofthe surface on which the groove 14 d is provided is not limited thereto.When the conductor spacer 14 is viewed in a plan view, for example, thecorner portions are cut or pressed on the inner side of the conductorspacer so that the conductor spacer 14 is generally in a cross shape,and the groove 14 d may be provided on the processed surface, asillustrated in FIG. 10.

Similarly, the shape of the groove 14 d on the side surface 14 c of theconductor spacer 14 can be variously changed, as illustrated in FIGS.11A to 11C. A modification example of the shape of the groove 14 d ofthe side surface 14 c of the conductor spacer 14 will be describedbelow. As illustrated in FIG. 11A, the groove 14 d may extend from theupper surface 14 a (the upper heat radiation plate 16 side) to the lowersurface 14 b (the semiconductor element 12 side) of the conductor spacer14. On the other hand, as illustrated in FIG. 11B, a length of thegroove 14 d may be relatively smaller than the length of the groove 14 dof the embodiment, and the groove 14 d extends to a length of the half(“half” includes “approximately half”) the length from the upper surface14 a of the conductor spacer 14 to the lower surface 14 b of theconductor spacer 14. In addition, the groove 14 d is not limited to alinear shape and may have a wavy line shape as illustrated in FIG. 11C,or another linear shape.

Although several specific examples have been described in detail above,these are merely illustrative and do not limit the scope of the claims.Technologies described in the claims include those in which the specificexamples above are variously modified and changed. Technical elementsdescribed in this specification or the drawings exhibit technicalusefulness alone or in various combinations.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor element; a first conductor bonded to an upper surface ofthe semiconductor element via a first solder layer; and a secondconductor bonded to an upper surface of the first conductor via a secondsolder layer, wherein the first conductor includes at least one grooveprovided in a stacking direction of the semiconductor element, the firstconductor, and the second conductor on a side surface adjacent to theupper surface of the first conductor, and wherein the at least onegroove of the first conductor extends to the upper surface of the firstconductor and does not extend to a lower surface of the first conductor.2. The semiconductor device according to claim 1, wherein the firstconductor includes the at least one groove in a range corresponding to acorner portion of the semiconductor element on the side surface of thefirst conductor.
 3. The semiconductor device according to claim 2,wherein the first conductor includes the at least one groove in at leastone corner portion among four corner portions of the side surface. 4.The semiconductor device according to claim 3, wherein the cornerportion is chamfered.
 5. The semiconductor device according to claim 3,wherein the corner portion is cut or pressed to have a cross shape whenthe first conductor is viewed in a plan view.
 6. The semiconductordevice according to claim 1, wherein the first conductor includes aplurality of grooves.
 7. The semiconductor device according to claim 1,wherein an angle formed by a fillet shape of a solder located betweenthe first conductor and the semiconductor element is smaller than 90°.8. A method of manufacturing a semiconductor device, the methodcomprising: solder-bonding a first conductor to an upper surface of asemiconductor element to form a laminate; and solder-bonding a secondconductor to an upper surface of the first conductor in the laminate,wherein: the first conductor includes at least one groove provided in astacking direction of the laminate on a side surface adjacent to theupper surface of the first conductor; the at least one groove extends tothe upper surface of the first conductor and does not extend to a lowersurface of the first conductor; and when the second conductor issolder-bonded to the upper surface of the first conductor, the secondconductor is disposed on the lower side of the laminate.